xfs: compile out v4 support if disabled

Add a few strategic IS_ENABLED statements to let the compiler eliminate
unused code when CONFIG_XFS_SUPPORT_V4 is disabled.

This saves multiple kilobytes of .text in my .config:

$ size xfs.o.*
text	   data	    bss	    dec	    hex	filename
1363633	 294836	    592	1659061	 1950b5	xfs.o.new
1371453	 294868	    592	1666913	 196f61	xfs.o.old

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index b022e5120dc42db424e79d101935bc23e9002dd0..283a5a26db3170f47059fbe323cb42a8935bc9fe 100644 (file)
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -332,19 +332,10 @@ static inline void xfs_add_ ## name (struct xfs_mount *mp) \
 __XFS_ADD_FEAT(attr, ATTR)
 __XFS_HAS_FEAT(nlink, NLINK)
 __XFS_ADD_FEAT(quota, QUOTA)
-__XFS_HAS_FEAT(align, ALIGN)
 __XFS_HAS_FEAT(dalign, DALIGN)
-__XFS_HAS_FEAT(logv2, LOGV2)
 __XFS_HAS_FEAT(sector, SECTOR)
-__XFS_HAS_FEAT(extflg, EXTFLG)
 __XFS_HAS_FEAT(asciici, ASCIICI)
-__XFS_HAS_FEAT(lazysbcount, LAZYSBCOUNT)
-__XFS_ADD_FEAT(attr2, ATTR2)
 __XFS_HAS_FEAT(parent, PARENT)
-__XFS_ADD_FEAT(projid32, PROJID32)
-__XFS_HAS_FEAT(crc, CRC)
-__XFS_HAS_FEAT(v3inodes, V3INODES)
-__XFS_HAS_FEAT(pquotino, PQUOTINO)
 __XFS_HAS_FEAT(ftype, FTYPE)
 __XFS_HAS_FEAT(finobt, FINOBT)
 __XFS_HAS_FEAT(rmapbt, RMAPBT)
@@ -358,6 +349,37 @@ __XFS_HAS_FEAT(needsrepair, NEEDSREPAIR)
 __XFS_HAS_FEAT(large_extent_counts, NREXT64)
 __XFS_HAS_FEAT(exchange_range, EXCHANGE_RANGE)
 
+/*
+ * Some features are always on for v5 file systems, allow the compiler to
+ * eliminiate dead code when building without v4 support.
+ */
+#define __XFS_HAS_V4_FEAT(name, NAME) \
+static inline bool xfs_has_ ## name (struct xfs_mount *mp) \
+{ \
+       return !IS_ENABLED(CONFIG_XFS_SUPPORT_V4) || \
+               (mp->m_features & XFS_FEAT_ ## NAME); \
+}
+
+#define __XFS_ADD_V4_FEAT(name, NAME) \
+       __XFS_HAS_V4_FEAT(name, NAME); \
+static inline void xfs_add_ ## name (struct xfs_mount *mp) \
+{ \
+       if (IS_ENABLED(CONFIG_XFS_SUPPORT_V4)) { \
+               mp->m_features |= XFS_FEAT_ ## NAME; \
+               xfs_sb_version_add ## name(&mp->m_sb); \
+       } \
+}
+
+__XFS_HAS_V4_FEAT(align, ALIGN)
+__XFS_HAS_V4_FEAT(logv2, LOGV2)
+__XFS_HAS_V4_FEAT(extflg, EXTFLG)
+__XFS_HAS_V4_FEAT(lazysbcount, LAZYSBCOUNT)
+__XFS_ADD_V4_FEAT(attr2, ATTR2)
+__XFS_ADD_V4_FEAT(projid32, PROJID32)
+__XFS_HAS_V4_FEAT(v3inodes, V3INODES)
+__XFS_HAS_V4_FEAT(crc, CRC)
+__XFS_HAS_V4_FEAT(pquotino, PQUOTINO)
+
 /*
  * Mount features
  *

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 5c9ba974252d16049fcf86c7184fb13e0885dee5..02c1a4aeaa4c3b90da86b6f582e2b42956510cdb 100644 (file)
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1580,17 +1580,21 @@ xfs_fs_fill_super(
        if (error)
                goto out_free_sb;
 
-       /* V4 support is undergoing deprecation. */
-       if (!xfs_has_crc(mp)) {
-#ifdef CONFIG_XFS_SUPPORT_V4
+       /*
+        * V4 support is undergoing deprecation.
+        *
+        * Note: this has to use an open coded m_features check as xfs_has_crc
+        * always returns false for !CONFIG_XFS_SUPPORT_V4.
+        */
+       if (!(mp->m_features & XFS_FEAT_CRC)) {
+               if (!IS_ENABLED(CONFIG_XFS_SUPPORT_V4)) {
+                       xfs_warn(mp,
+       "Deprecated V4 format (crc=0) not supported by kernel.");
+                       error = -EINVAL;
+                       goto out_free_sb;
+               }
                xfs_warn_once(mp,
        "Deprecated V4 format (crc=0) will not be supported after September 2030.");
-#else
-               xfs_warn(mp,
-       "Deprecated V4 format (crc=0) not supported by kernel.");
-               error = -EINVAL;
-               goto out_free_sb;
-#endif
        }
 
        /* ASCII case insensitivity is undergoing deprecation. */